Field of the Invention
The disclosed subject matter generally relates to reclosable fasteners with sliders particularly suited for thermoplastic bags and the like. Particularly, the disclosed subject matter relates to a track and slider configuration with increased strength and flexibility and reduced size.
Description of Related Art
Plastic bags are in widespread use in a varied and diverse number of household and commercial applications, especially in the food packaging industry. One advantage of plastic bags is their ease of opening and resealing. Some of these bags are reclosable via the use of a reclosable feature such as a reclosable fastener. In many bags, the fasteners can be opened and closed either by pressure or by the use of an auxiliary slider mechanism.
Generally, two types of such reclosable fasteners exist—(i) push to close (“PTC”) and (ii) zipper. The PTC fastener requires the application of an external force to open or close the engageable tracks, whereas the zipper fastener relies upon a slider for opening or closing the rib and groove elements. As such, the profile configuration of the reclosable track of a zipper fastener often differs from that of a PTC fastener.
In the manufacture of thermoplastic film bags, a pair of male and female fastener elements or tracks extend along the mouth of the bag and these male and female elements are adapted to be secured in any suitable manner to the flexible walls of the thermoplastic film bag. These elements may be integral marginal portions of such walls or the elements may be extruded separately and thereafter attached to the walls along the mouth of the bag. U.S. Pat. Nos. 5,007,143 and 8,087,826, each of which is incorporated by reference in its entirety, describe one type of zipper profile in which the cross-sectional shape of the zipper is such that the male and female elements can be engaged or closed by pressing the bottom together first, then rolling it closed toward the top. This configuration is referred to as a “rolling action” reclosable fastener.
Furthermore, various arrangements have been utilized heretofore to maintain auxiliary slider mechanisms on fasteners. One arrangement which has been used to prevent or inhibit the slider mechanism from going past the ends of the fastener and coming off of the bag is to incorporate opposing end termination clips at the ends of the fastener. The use of end termination clips, however, increases the cost of producing the bag as it requires an additional component on the bag and an additional piece of equipment in order to place the end termination clips on the bag. In addition, the placement of end termination clips on the ends of the fastener involves an additional processing step which may not be desirable when manufacturing speeds are important.
To avoid using end termination clips to prevent or inhibit the auxiliary slider mechanism from going past ends of the fastener, an alternative arrangement has been employed which involves shaping material from the fastener into opposing end stops or end stop structures which protrude from the fastener or zipper and engage the slider mechanism to prevent or inhibit it from going past the respective ends of the fastener. U.S. Pat. Nos. 7,267,856 and 7,669,307, each of which is incorporated by reference in its entirety, describe one technique to shape end stop structures by ultrasonically smashing the opposite ends of the male and female profiles of the fastener to form the protruding end stop structures.
However, there remains an opportunity to improve the seal strength of such conventional fasteners, yet provide a fastener with increased flexibility, for example to permit the fasteners to be easily opened and closed on overstuffed bags. Additionally, there remains an opportunity to provide a fastener with reduced size that can be formed using less material than conventional fasteners.